| Author | Message | ||
| Dustin Bringham (Dmbringham)
Registered Member Username: Dmbringham Post Number: 1 Registered: 2-2009 Posted From: 98.162.238.75 Rating: N/A |
I have a 1977 MC-8. The bus seems to top out at around 50-55mph, everything else is working fine. I can have my foot to the floor, and it will not go above 55mph. It has a DD 8V-71 with an Allison HT-740. I purchased the bus about 2 weeks ago from a school system; they kept the bus immaculate, and very detailed records of everything; when I went to test drive the bus it ran 70mph with no problems, but when I purchased the bus, and drove it home this started. Any thoughts?? | ||
| Dan West (Utahclaimjumper)
Registered Member Username: Utahclaimjumper Post Number: 155 Registered: 1-2005 Posted From: 208.66.38.115 Rating: N/A |
Time to change fuel filters.>>>Dan | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 725 Registered: 8-2006 Posted From: 64.55.111.6 Rating: N/A |
Welcome Dustin, To an affliction without a cure. A guess would be plugged fuel filters. Power takes fuel, very simple. Could also be a suction leak, or partially collapsed line between the tank and the engine. Are you sure the trans is shifting properly? You should feel 4 shifts, even though it is only a 4 speed trans, as the converter lockup which occurs in 2nd gear feels like a shift. I guess we need to know if it accelerates as well as it did from a stop? Good luck, post back with what you find, and we'll figure it out. Air throttle, or mechanical linkage? George | ||
| Jack Conrad (Jackconrad)
Registered Member Username: Jackconrad Post Number: 963 Registered: 12-2000 Posted From: 71.54.29.215  Rating: N/A |
Make sure your transmission is in D and not 3. Indicator on shift lever could be off slightly. If you are sure it is in D, replace the fuel filters. Tip: replace primary filter first (closest to rear bumper of the bus), fill new filter with fresh clean fuel before installing. After installing, start engine, revving it up as soon as it starts. Shut engine off and follow same procedure to change secondary filter. Changing filters this way will make it less apt for you to loose prime. Look at the fuel line into coming into the primary filter from the bulkhead in the front of the engine compartment. If there is a shut off valve in this line, close it before changing each filter and open before re-starting the engine. Jack | ||
| Buswarrior (Buswarrior)
Registered Member Username: Buswarrior Post Number: 1494 Registered: 12-2000 Posted From: 76.66.19.143  Rating: N/A |
My money is on the transmission being in 3rd. 3rd and 4th share the same plane on the shifter, was it nudged forward? happy coaching! buswarrior | ||
| Clint Hunter (Truthhunter)
Registered Member Username: Truthhunter Post Number: 27 Registered: 1-2009 Posted From: 24.129.235.190 Rating: N/A |
always real good to know what gear im am in and it deosn't hurt to know my all my filters and fluids are good ! | ||
| Dustin Bringham (Dmbringham)
Registered Member Username: Dmbringham Post Number: 2 Registered: 2-2009 Posted From: 98.162.238.75 Rating: N/A |
Well I don't think it was in 3rd, but the shifter does not have any markings; so I can't say for sure. | ||
| Keith Wood (Ft6)
Registered Member Username: Ft6 Post Number: 83 Registered: 8-2008 Posted From: 75.209.63.131 Rating: N/A |
Try coming OFF the pedal a bit, see if it shifts up. You may be forcing a kickdown into passing gear. | ||
| don goldsmith (Bottomacher)
Registered Member Username: Bottomacher Post Number: 235 Registered: 12-2000 Posted From: 72.15.86.59 Rating: N/A |
From neutral, merely push the shifter forward slowly until the trans engages. Travel at the BASE of the shifter should be about 3/4" into the first notch. | ||
| Doyle Gaither (Texasborderdude)
Registered Member Username: Texasborderdude Post Number: 174 Registered: 3-2007 Posted From: 75.210.61.78 Rating: N/A |
Don't forget the air filter too. A clogged air filter can sure cost you power. Smoke? What color? An 8V71 with an HT740 sure ought to top out around 70 on the flat. dg | ||
| Dustin Bringham (Dmbringham)
Registered Member Username: Dmbringham Post Number: 3 Registered: 2-2009 Posted From: 98.162.238.75 Rating: N/A |
We have had some nasty weather here this week, but I will try all of this first thing in the morning. There is no smoke at all coming from the motor. I'll keep you all posted, and thanks again! | ||
| Dustin Bringham (Dmbringham)
Registered Member Username: Dmbringham Post Number: 4 Registered: 2-2009 Posted From: 98.162.238.75 Rating: |
The shifter was off a little so it looks like I was in 3rd instead of drive. I Still Changed the fuel filters, and air filter, and seems to be running great. Thanks for all the help; I'm sure I will have a million more! | ||
| Clint Hunter (Truthhunter)
Registered Member Username: Truthhunter Post Number: 42 Registered: 1-2009 Posted From: 24.129.235.190 Rating: N/A |
I recall more than one stretch of road ,finaly realizing why I was not able to get up to speed despite a heavy load on the near level load, only to finaly realize ( Opps ) the shiter wasn't put back in D after that last small town. My favorite kind of bus repair. Takes some getting use too, having the noisy bits at the rear of the bus. | ||
| Jack Conrad (Jackconrad)
Registered Member Username: Jackconrad Post Number: 965 Registered: 12-2000 Posted From: 71.54.29.215 Rating: N/A |
Glad to hear it was nothing major. I have done the same thing. When driving through a small town at 35-45 MPH, I put transmission in 3rd to prevent frequent shifting between 3rd & 4th. Sometimes forget to shift back into 4th when leaving town. I now usually keep my right hand on the shifter until I am back in 4th. Jack (Message edited by JackConrad on February 17, 2009) | ||
| David Dulmage (Daved)
Registered Member Username: Daved Post Number: 233 Registered: 12-2003 Posted From: 142.46.199.30  Rating: N/A |
I've done the same thing. It was a little disconcerting until I figured out what was wrong. DaveD |
